Wednesday, October 3, 2012

The Nutcracker

The anterior pararenal space is tight real estate.  Of the many vascular structures in this area, one vessel in particular has to make a reach over and through multiple other structures to reach its destination... the left renal vein.  The left renal vein also acts as the final common conduit for multiple other draining veins including the left gonadal vein, left adrenal vein, left lumbar veins, and left inferior phrenic vein... so narrowing at the downstream left renal vein can result in dilatation of these upstream veins formation of varices, and renal venous hypertension.

If a mass were compressing the renal vein at this point, then the etiology and the downstream effects are usually straightforward... but occasionally, if a patient's thorax has a narrow AP diameter, the left renal vein can be compressed between the superior mesenteric artery and the aorta, like a nutcracker.

Below is an example:

59 Y lady receiving an arterial runoff study for lower extremity disease, found to incidentally have dilatation of the left ovarian vein and venous congestion in the pelvis.

The patient below was receiving an MRA of the chest and abdomen to rule out an aortic aneurysm (which was not present), but likely due to her narrow AP diameter, there was asymptomatic compression of her left renal vein with more prominent dilatation of the left lumbar veins than the left gonadal vein.

38Y lady with a negative exam for evaluation of aortic aneurysm. Incidental compression of the left renal vein and dilatation of the left ovarian and left lumbar veins

Another opportunity for compression of the left renal vein occurs with the retroaortic left renal vein:

Although the "nutcracker" morphology may exist, it only becomes a "syndrome" if there are associated clinical symptoms such as flank pain, left-sided varicocele, hematuria, chronic fatigue, or even autonomic dysfunction.  Severely symptomatic left renal nutcracker phenomenon has been treated with transposition of the left renal vein (below)

The term "nutcracker syndrome" also refers to a similar situation in the retroperitoneum in which a narrow AP diameter results in the duodenum being crushed between the aorta and superior mesenteric artery, resulting in obstruction.

1. Duty B, Daneshmand S. "Venous Resection in Urological Surgery." The Journal of Urology. 180:6, Dec 2008, pp 2338-2342.
2. Hohenfellner M, D'Elia G, Hampel C, et al. "Transposition of the Left Renal Vein for the Treatment of the Nutcracker Phenomenon: Long Term Follow-up" Urology. 59:3, March 2002, pp 354-357.
3. Rudloff U, Holmes RJ, Prem JT, et al. "Mesoaortic Compression of the Left Renal Vein (Nutcracker Syndrome): Case Reports and Review of the Literature" Annals of Vascular Surgery. 20:1, Jan 2006, pp 120-129.